Rotary beam antenna



Jan. 6, 1942. G. H BROWN 6 266,640

ROTARY BEAM ANTENNA Filed Nov. l5, 1940 Snventor Patented Jee. e, 1 942 UNITED STATES i .PATENT ao'raar BEAMANTENNA L George B. Brown, Haddoniicld, N.'J.', assigner to v Badio'Corpontion o! America; a corporation ot Delaware Application November l5. Nil-:335.743 l 13 claims (ci. 25o-41) i This invention relates toradio beam antennas and particularly to aradio beam antenna in'- cluding'means vfor operating the same at either of two related wave lengths.

vagin. s. Patent. No. 1,745,342 describes el system in which a driven antenna is coupled; to a parasitic director and a parasiticreilector which are parallel to and respectively infront of and behind the antenna. Such a system is directive and efficient. However, it is only eilicient within a narrow frequency range about the resonant point of the antenna.

reflector l ior'the longer vwave is slightly more It is an' object-of the 'presentinvention to at either of two wave lengths.'v lAnotlierjobjectis to provide a beam antenna which may be operated at two related frequencies by means of an automatically selective circuit. An additional object'is to provide-means whereby a rotary beam antenna may be operatedA at either .of two wave lengths bearing a two to one ratio. The vinvention will'be described'by vreferring to the accompanying drawing injwhich Fig. 1

. provide means for operating -a directive antenna is a perspective view o! one embodiment -of the f rotary beam antenna of the inventiom' Fig. 2l is av perspective view of therotating mechanism of Fig. 1 ;"Fig. 3 is a schematic circuit diagram" of the antenna of Fig. 1;'Flg. l3Aia"afrcircuity diagram of a portion of Fig. k3;. and'fFlgs-.4A;

4B, 4C, 4D and 4E are circuit diagramsjof 'modi-fvk proximatel'y one-eighth wavelength behindthe antenna conductor ikwhich has Aan effective length of'half the longer wave. The director g 5 forl the longer waveis` slightly less than-a. half kwave long' andl isv spaced approximately oneeighth wave length in front of the antenna con'- ductor. For the .shorter-fwav'esthe lreflector 3 -and the director' lare spacedjone-eighth of the shorter wave length-behind andfjahead respectively. of the vantennaconductor 5.j The short wave reilector (is sligl itly y longery andi the short wave director is* slightly 'shorter-than ;a `half of the shorter wave length..`

Since the longer wave is. twice'slthelengthof the shorter, it follows that -the' shorter wave elements willA` have no-.appreciable eiec't'on the y longer wave elements. The antennaconductor `5v operates as a' half wave ydipole for', t h e longer waves, and as ctwohalf-y wave cophased dipoles for the shorterwaves. v I

v' I'he transmissionline 2 5; as statedffis con- 'nected to fthe. antenna conductor at v.points inrsuring` af proper match-for .the longerjwaves The problemi remaining is provide means whereby the antennalfmr'iy`VV function automat-- icallyand efilciently. at` 'either theflnger or Similar reference characters will similar elements in the drawing.

Referring to Fig. l an antenna arrayinclud ing reflectors i, I, antenna 5, and directors 1.5-`

are suitably secured to a supporting member Il which may be a conductor. I'I'he 'supporting member n is fastened te a,ered1e '|s, whiehfl' is mounted on the rotating mechanism shown-j in Fig. 2. The rotating mechanism includes a plate I5 for supporting the-cradle by means of pins or bolts |1, lo, Either belt .may be withdrawn to tilt the antenna array .toward-thever- The antenna .'i is connected to s tical plane. slip rings 2|, 23 by av transmission line v25. The

transmission line is connected to the'antenna include, for long wave operation'A an impedanceff' matching portion. The antenna array may be@ rotated by means'of a motor v-21, "connected' through gearing 25 to the supportingshaft'i.: -While la. power mechanism is preferable, anyrotational means may be employedirt'hebeam is to be directed inthe azimuth. Y Ws v relation of the conductors of the array.

The schematic diagram of"liig. 3v

at 'the shorter wavelength.

shorter'wave length; maybe ac :oililished in anumber oiarrangementslof whichthefol- 'is-.preferredj. A: matching stub .I lji's conzjs et the-stub al In somexnsteuetie nl collector rings l.will provide vsu'iilicier'it vanacity.l

ist'ub' :l and' associated capacity preallel resonant at 14.2 megacycles and at 29 megacycles the inductive stub is only effective since.

the input reactance of the open section becomes extremely high. In Fig. 4C the stub acts like aninductive stub 13 inches in length at the high frequency and as a high impedance at the lower frequency. In Iig.` 4D the circuit LC becomes series resonant at 2 9 megacycles and hence'places an inductive stub of the proper length across the line; at 14.2 megacycles the circuit LC becomes parallel resonant and the input reactance of the stub across the 4line becomes very high. In Fig. 4E the circuit constants are chosen so that the combination acts as an inductive stub of the correct length at the high frequency and as a high impedance at the low frequency.

Thus the invention has been described a"s a rotating beam antenna which may be operated for receiving or transmitting waves of a predetermined length ratio. for example l0 meters and 20 meters. v The antenna conductor is used as a pair` of cophased half wave dipoles atthe short wave length and as a half wave dipole at thelonger wave length. Bv means of one of a number of novel transmission line connections the antenna is matched to the line forpwaves of eitherl length. No switching is required for either short or long wave operation. The several dimensions, wave lengths, or frequencies have been cited by way of illustration rather than imitation. Furthermore, it has been found that theautomatic operation is entirely satisranges. Renectors and/or directors may be used to make the beam sharply directive although either or both may b e omitted on either wave length range to make the pattern less directive. The receiver or transmitter which is associated with ,the antenna is simply tuned to either wave length band.

4. A combined long and short wave rotaryv beam antenna including an antenna .conductor having a length equal to said short wave and to half said long wave, a long wave reflector spaced behind said antenna conductor, a trans-- mission line connected to said antenna conductor and terminated in a proper impedance for the application of currents corresponding to said long wave, and means connected to said transmission line for matching said line to said antenna conductor for currents corresponding to said short wave without altering substantially said termination impedance for long wave currents. v

5. A combined long and short wave rotary beam antenna including an antenna conductor having a length equal to said short wave and to half said long wave, a long wave 'reflector spaced behind said antenna conductor, a long wave director spaced in front of said antenna :conductor, a tron line conncctedto said antenna conductor and terminated in a proper impedanee forthe application' of currentscorresponding to said long wave, andmeans connected to saidtransmission line for matching said line to said antenna conductor for currents corresponding to said short wave without altering "factory over a band of wave lengths in both pedance at the long wave length, and means con- I nected to said transmission line for matching the impedance at said short length so thatsaid line is properly terminated for either wave.v

2. A combined long and short wave antenna including an antenna conductor having a length equal to said short wave and to half said long wave.A a'-transmission line connected to said antenna conductor and terminated in a proper impedance for the application of currents of said line is properly terminated for said long and short waves.

. 3. A combined long and short wave rotary beam antenna including an antenna conductor having a length equal to said short wave and to half said long wave, a transmisison line connected to said antenna conductor and terminated in a proper impedance for the application of curlong wave. and means connected to said trans- ,n

mission line to terminate the line properly for substantially said tron impedance for long wave currents. t

6. A combined long and short wave rotary beam antenna including an antenna conductor having a length equal to said short wave and to half said long wave, a short wave reector spaced behind'said antenna conductor, a' transmission line connected to said antenna conductor and terminated in a proper impedance for the application of currents corresponding to said long wave, and means connectedto said transmission line for matching said line tosaid antenna conductor for currents correspiding to said shortwave without altering substandauy said termlnation impedancefor long wave currents.

7. A combined long and short wave rotary beam antenna includingran antenna conductor having a length equal to said short wave and to half said long wave, a short wave reflector spaced behind said antenna conductor, a short wave director spaced in front of said antenna conductor, a transmission line connected to said antenna conductor and terminated in a proper impedance for the application of currents corresponding to saidlong wave, and means connected to said transmission line for matching said line to said antenna conductor for currents corresponding to said short wave without altering substantially said termination.Z ,impedance for long wave currents.

8. A combined long and short wave rotary beam antenna including an antenna conductor having a length equal to said short wave and to half said long wave, a long wave reector spaced behind said antenna conductor, a short wave reiiector spaced between said long wave reflector and said antenna conductor, a long wavedirector spaced in front of said antenna conductor, a short wave director spaced between said antenna conductor and said long wave director, a transmisapplication of currents corresponding to said long wave, and means connected to said transmission line for matching said line to said antenna conductor for currents corresponding to said short A wave without altering substantially said termination impedance for long wave currents.

9. An antenna of the character of claim 3 in which said reiiectors and directors are arranged parallel to each other and are in the same plane and are supported by a conductive member located at the centers of said reiiectors and directors.

10. An antenna of the character of claim 8 in which said reilectors and directors are arranged parallel to each other and are in the same plane and are supported by a conductive member located at the centers of said reectors and directors.

11. A combined long andl short wave rotary beam antenna including an antenna conductor having a length equal to said short wave and to hall. said long wave, a transmission line connected to said antenna conductor and terminated in a proper impedance for the application of currents corresponding to one o! said waves, and means connected to said transmission line for matching said line to said antenna conductor for currents corresponding to the other of said waves without altering substantially said termination impedance for said one wave.

12. A combined long and short wave rotary beam antenna including an antenna conductor having a length equal to said short wave and to` half said long wave, a long wave reflector spaced behind said antenna conductor, a long wave director spaced in front of said antenna conductor, a transmission line connected to said antenna conductor and terminated in a proper impedance for the application of currents corresponding to one of said waves, and-means connected to said transmission line for matching said line to said antenna conductor for currents corresponding to the other of said waves without altering substantlally said termination impedance for said one wave.

13. A combined long and short wave rotary beam antenna including an antenna conductor having a length equal to said short wave and to half said long wave, a long wave reflector 'spaced behind said antenna conductor, a short wave reflector spaced between said long Wave reflector and said antenna conductor, a long wave director spaced in front of said antenna conductor, a short wave director spaced between said antenna conductor and said long wave director, a transmission line connected to said antenna conductor and terminated in a proper impedance for the application of currents corresponding to one of said waves, and means connected to said transmission line for matching said line to said antenna conductor for currents corresponding to the other of said waves without altering substantially said termination impedance for said one wave.

` GEORGE H. BROWN. 

